Crown indicators and their relationship with acid deposition : forest health monitoring case study in Baltic states

Abstract

Primary (crown density, foliage transparency) and integrated (total crown losses) tree crown indicators according to Forest Health Monitoring (FHM) program have been chosen as the main parameters indicating forest health in the Baltic States. Geographical Information System Arc Info has been used for the analysis of spatial changes of these indicators and their relations with acid deposition (sulfur and nitrogen). It is determined that northward increase of crown density of Scots pine (Pinus sylvestris) and birch (Betula spp.) is statistically significant (P<0.05). Data on total crown losses of the main tree species and groups demonstrate a clear trend along geographical gradient, decreasing from south to north. Deposition of sulfur and nitrogen tend to decrease distinctly in the same direction. It was determined that the correlation between the FHM crown indicators and deposition is not strong, however, in most cases, statistically significant (P<0.05). The correlation between deposition and Scots pine crown indicators (primary and integrated) indicated the greatest statistical significances. The relations of total crown losses with sulfur deposition occurred to be stronger than with nitrogen